This invention relates to incandescent sources of visible radiations and, more particularly, to a refractory oxide incandescent source of visible radiations which selectively emits visible radiations while scattering infrared radiations, which scattered infrared radiations contribute to the generation of more visible radiations.
Refractory-oxide incandescent lamps are known, such as generally described in U.S. Pat. No. 3,412,286, dated Nov. 19, 1968. Such refractory oxide incandescent radiators are not specially constructed to selectively emit visible while scattering infrared radiations, and the efficiency of these radiators is not as good as desired.
The well-known Wellsbach mantle is initially formed as a silk or cotton fiber mantle-shaped support which is impregnated with ceria-doped thoria. The impregnating material remains in self-sustaining mantle form when the silk or cotton fiber is burned off. Apparently the mantle owes its bright appearance to its very high emissivity in the visible spectrum, although the emissivity of thoria in the infrared region of the spectrum is very low.
In copending application Ser. No. 552,834 filed Feb. 25, 1975 by R. W. Warren, one of the coinventors herein and owned by the present assignee, is disclosed a thermal collector of solar energy wherein a powdered, elemental semi-conductor absorbs the solar energy and longer wavelength re-radiation of absorbed energy is greatly reduced by the use of the powered layer which scatters and does not absorb the longer wavelength radiation, thereby permitting operation at a high temperature such as 300.degree.C. The present incandescent source operates at a much higher temperature, such as 2000.degree.C.